NGC 6331 is a type E[1] elliptical galaxy located in the Ursa Minor constellation.

[2][1] It is located 737 million light-years from the Solar System[3] and was discovered by German-British astronomer William Herschel on December 20, 1797, utilizing an 18.7-inch f/13 spectrum telescope[4] but also observed by Guillaume Bigourdan.

[5] With an approximate diameter of 345,000 light-years, NGC 6331 is well considered one of the largest galaxies.

[3] It is the brightest group member of Abell 2256 and first in 6' string to the east, making up of 6 galaxies.

[6] NGC 6331 also makes up a part of the galactic triplet CGCG 355-024[7] which comprises two other elliptical galaxies in the cluster, CGCG 355-024 NED03 (PGC 59513)[8] and CGCG 355-024 NED01 (PGC 84827).